On television, he played Officer Bill Gannon with a phlegmatic but light touch to Jack Webb’s always-by-the-book Sgt. Joe Friday in the updated “Dragnet,” from 1967 to 1970. He starred as Pete Porter, a harried husband, in the situation comedy “Pete and Gladys” (1960-62), reprising a role he had played on “December Bride” (1954-59). He was also a regular on “The Richard Boone Show” (1963-64), “Kentucky Jones” (1964-65), “The D.A.” (1971-72), “Hec Ramsey” (1972-74) and “Blacke’s Magic” (1986).

But to many fans he was first and foremost Col. Sherman T. Potter, commander of the 4077th Mobile Army Surgical Hospital unit in Korea. With a wry smile, flat voice and sharp humor, Mr. Morgan played Colonel Potter from 1975 to 1983, when “M*A*S*H” went off the air. He replaced McLean Stevenson , who had quit the series, moving into the role on the strength of his performance as a crazed major general in an early episode.

“It was very peaceful,” his daughter, Michele Lesser, told CNN, saying the family had hoped for a quick and painless death. “He was a great grandpa, and an amazing father. He had a heart of gold — and a sense of humor of platinum.”

Best known as Jerry Seinfeld’s Uncle Leo on TV’s “Seinfeld,” Lesser made more than 500 film, television and stage appearances. His TV roles ranged from “Studio One in Hollywood” in 1949 to a 2009 role on “Castle.”

Highly intense, with a bulbous nose, high cheekbones and ruddy complexion, the actor was immediately recognizable in films ranging from the second “Jurassic Park” movie to “Romeo + Juliet.”

It was for his role as Daniel Day-Lewis’s father in the IRA drama “In the Name of the Father” that he got his only Oscar nomination, for best supporting actor. He lost out to Tommy Lee Jones for “The Fugitive.”

He also starred in the British brass band movie “Brassed Off,” and worked with Steven Spielberg on the slave revolt story “Amistad.”

Spielberg reportedly called him “the best actor in the world,” prompting Postlethwaite to respond that what the director actually said was that he “thought he was the best actor in the world.”

Henry Winkler and Scott Baio — who both co-starred with Tom Bosley on “Happy Days” — tell TMZ they are both shocked by his death … but remember their former castmate as a “great man.”

Winkler tells us, “I saw him before I ever got to Hollywood on Broadway, and he was great. And then I got to act with him for 10 years and he was great. Tom Bosley was our mentor. He was a true artist … a great husband, and a fabulous father and grandfather. He will be sorely missed, but never forgotten.”

His first wife was actress Janet Leigh of “Psycho” fame; actress Jamie Lee Curtis is their daughter.

“My father leaves behind a legacy of great performances in movies and in his paintings and assemblages,” Jamie Lee Curtis said in a statement Thursday. “He leaves behind children and their families who loved him and respected him and a wife and in-laws who were devoted to him. He also leaves behind fans all over the world.”

Curtis struggled against drug and alcohol abuse as starring roles became fewer, but then bounced back in film and television as a character actor.